JP3208982B2 - Optical fiber device for laser transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber device for laser transmission used in a laser beam machine, and more particularly to an improvement in a device for detecting a disconnection when an optical fiber is disconnected and cutting off a laser beam. .

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a configuration diagram of a conventional optical fiber device for laser transmission disclosed in Japanese Unexamined Patent Publication (Kokai) No. H10-15095. In FIG. 1, reference numeral 1 denotes a power laser light source such as an Nd: YAG laser or a CO ₂ laser. A power laser light 2 emitted from the laser light source 1 passes through a mirror 4 via a shutter mechanism 3 interposed in an optical path. The light is condensed on the incident end face of the optical fiber 6 by the condenser lens 5. The mirror 4 allows invisible light to pass through,
Visible light is a reflecting mirror and therefore Nd: YA
Power laser beams such as a G laser and a CO ₂ laser pass through. 9 is a visible light 7 emitted from the input end of the optical fiber 6.
(For example, a phototransistor or a photodiode) that receives light through the condenser lens 5, the mirror 4 and the filter 8. The detector 9 is connected to an input terminal of an amplifier 10, and an output terminal of the amplifier 10 is connected to one input terminal of a comparator 12 via a resistor 11a. The other of the resistor 11b, one of which is connected to the ground, is connected between the resistor 11a and the comparator 12. The filter 8 blocks stray light of the power laser light 2 and allows the visible light 7 to pass. A reference value circuit 13 for generating a reference voltage is connected to the other input terminal of the comparator 12. The output terminal of the comparator 12 is a shutter driving circuit 1
The shutter drive circuit 14 is operated by an output signal from the comparator 12 and closes the shutter mechanism 3 interposed in the optical path of the power laser light 2 to cut off the irradiation of the power laser light 2.

Next, the operation will be described. Now, it is not noticed that the middle part of the optical fiber 6 is broken or the entrance end face or the exit end face of the optical fiber 6 is damaged.
When the power laser beam 2 is irradiated,
Scattering and reflection of the power laser light 2 occur, and the polymer-based coating material 6a of the optical fiber 6 at the defective portion burns and emits light. The emitted visible light (hereinafter referred to as secondary light 7) enters the optical fiber 6. The light exits from the end face in reverse. The emitted secondary light 7 passes through the condenser lens 5, is reflected by the mirror 4, passes through the filter 8, and is received by the light receiving detector 9. The light receiving detector 9 converts the output of the secondary light 7 into an electric signal and sends it to an amplifier 10. The electric signal of the secondary light 7 amplified by the amplifier 10 is compared with the voltage of the resistors 11a and 11b. Is input to The voltage of the secondary light 7 input to the comparator 12 is compared with a reference voltage of a set level from the reference value circuit 13, and when the voltage of the secondary light 7 reaches the level of the reference voltage, the voltage of the comparator 12 An electric signal is sent from the output terminal to the shutter drive circuit 14 and the shutter drive circuit 14
Operates and closes the shutter mechanism 3 to close the power laser beam 2
Cut off the irradiation.

[0004]

Since the conventional optical fiber device for laser transmission is constructed as described above, the power laser light from the optical fiber emitting end is condensed by the processing lens to cut the workpiece (metal). In the case of welding, the processed portion emits light, and the emitted visible light (hereinafter referred to as “return light”) returns along the optical path from which the power laser light is emitted, that is, the processed lens, the optical fiber emitting end, the optical fiber 6, the optical fiber incident end, The light is received by the light receiving detector 9 via the optical lens 5 and the mirror 4. For this reason, in the conventional method of detecting the secondary light, which is visible light, the workpiece emits light, and it is not possible to discriminate between the visible light received by the light receiving detector 9 and the visible light received by the light receiving detector 9 due to a defect in the optical fiber. Therefore, there is a problem that a trouble of the optical fiber cannot be detected.

In addition to the secondary light, a fusible conductor such as lead or solder is wound around the outer periphery of the optical fiber (Japanese Patent Laid-Open No. 58-130301), or a conductive paint is coated on the surface of the optical fiber with a required width ( JP-A-60-13
No. 9241), when the optical fiber is disconnected, it is electrically detected that the optical fiber is burned out by the thermal action of the light energy of the laser light scattered and leaked from the break point and is disconnected, and the oscillation of the laser light is stopped. Was. By the way, the fusible conductor and the conductive paint have a small thickness (for example, 25 μm) in view of promptly fusing when laser light is scattered or leaked.
In addition, the former has high electrical resistance because it is a paint, although the former contains lead and solder and the latter contains metal powder. For this reason, when detecting a disconnection, when a large current is applied, the fuse is cut off by self-heating, so that it must be detected with an extremely small current, and the disconnection detection circuit becomes complicated. Further, when the optical fiber is long, disconnection detection becomes extremely difficult.

When a fusible conductor is used, it is necessary to wind the fusible conductor on the optical fiber without gaps in order to eliminate disconnection detection leakage. Accordingly, the length of the fusible conductor becomes longer and the electric resistance becomes higher, so that it becomes more difficult to detect disconnection.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. When cutting or welding metal with a power laser beam, it is possible to detect a trouble such as an optical fiber disconnection and cut off the power laser beam. An object is to obtain an optical fiber device for laser transmission.

[0008]

SUMMARY OF THE INVENTION An optical fiber device for laser transmission according to the present invention comprises: an optical system for transmitting laser light through an optical fiber, irradiating a workpiece with laser light, and processing the laser light; When a failure occurs in the transmission path, the visible light emitted from the optical fiber is detected, and when the detected visible light reaches the detection level of the secondary light indicating the visible light emitted from the abnormal portion, the laser is emitted. In a laser transmission optical fiber device having a means for blocking light, a laser beam is transmitted, and a visible light selective reflection means for reflecting visible light emitted during processing of a workpiece is provided between a laser light emitting end of the optical fiber and the workpiece. It is provided between them.

The visible light selective reflection means comprises a high-refractive-index thin film formed on an optical glass, a low-refractive-index thin film and a high-refractive-index thin film alternately stacked, and a high-refractive-index thin film on the outermost side. Wherein the product of the light refractive index and the film pressure of each thin film is a high light refractive index body in contact with the optical glass and a thin film of the high light refractive index body formed on the outermost side. Is ８ of the wavelength of visible light emitted during processing, and in the remaining thin film, is １ of the wavelength of visible light.

[0010] The visible light selective reflection means may comprise a high-refractive-index thin film formed on optical glass, alternately stacking a low-refractive-index thin film and a high-refractive-index thin film. A low-refractive-index body and a high-refractive-index body having a difference in refractive index in the range of 2.90 to 4.16,
The total number of thin films is in the range of 19 to 40.

Further, the laser light is transmitted by an optical fiber,
In a laser beam machine that irradiates a workpiece with laser light and processes it, a protective film is coated so that the laser light does not scatter outside, and the entire surface of the optical fiber through which the laser light is transmitted is insulated between metal foils. Covering with a sheet with a plate interposed, applying a voltage between the metal foils, detecting a change in resistance between the metal foils, and having means for shutting off a laser beam when the resistance reaches a predetermined level. It is.

Further, a laser beam anti-reflection member for absorbing laser light is formed on the optical fiber side surface of the metal foil located on the optical fiber side of the metal foil.

[0013]

An optical fiber device for laser transmission according to the present invention transmits an optical fiber for transmitting a laser beam and cuts and welds a workpiece, and a secondary light as visible light emitted from an incident end of the optical fiber. When the detected secondary light reaches a predetermined level, the laser light is transmitted almost 100% in a device that cuts off the laser light when the secondary light reaches a predetermined level, and the visible light reflects the return light in the visible region from the cut / welded portion. Even if the light selective reflection means is provided between the optical fiber emitting end and the workpiece, the disconnection of the optical fiber is reliably detected without being affected by the returning light.

The product of the optical refractive index and the film thickness on the surface of the optical glass is λ / 8, λ / 4, λ / 4... Λ / 4, λ / 4,
Thin films of a high-refractive-index body and a low-refractive-index body are alternately laminated so as to have a wavelength of λ / 8, and light in a visible light region emitted from the workpiece is selectively reflected.

In order to cut back light in the visible region from the cut / welded portion of the workpiece, optical glass is formed by alternately forming a high-refractive-index thin film and a low-refractive-index thin film. In the range of 2.66 to 4.16, and the total number of the thin films is in the range of 19 to 40, the return light can be cut and the disconnection of the optical fiber can be detected with high accuracy.

Further, the laser light is transmitted by an optical fiber,
In a laser processing machine that cuts and welds a workpiece, two adjacent insulated conductors are arranged on a surface coated with an optical fiber through which laser light is transmitted by rubber or plastic, and a voltage is applied between the insulated conductors. By applying the applied voltage and detecting a resistance change between the insulated conductors, the disconnection of the optical fiber is detected, and the laser beam is cut off when the resistance reaches a predetermined level.

Further, the laser light is transmitted through an optical fiber,
In a laser processing machine that cuts and welds a workpiece, the entire surface of an optical fiber coated with an optical fiber through which laser light is transmitted by rubber or plastic is covered with a sheet having an insulating plate interposed between metal foils. A voltage between the metal foils, a change in resistance between the metal foils is detected, and means for cutting off laser light when the resistance reaches a predetermined level is provided. Optical fiber disconnection can be detected with high accuracy.

Further, in the sheet in which an insulating plate is interposed between the metal foils, the antireflection member is provided on the optical fiber side surface of the metal foil located on the optical fiber side among the metal foils, so that the laser beam can be reliably transmitted. Absorb.

[0019]

[Embodiment 1] FIG. 1 is a configuration diagram showing an optical fiber device for laser transmission according to Embodiment 1 of the present invention. Reference numerals 1 to 14 are the same as those in the conventional case, and a description thereof will be omitted. Reference numeral 15 denotes a visible light selective reflection means that reflects visible light and transmits almost 100% of the power laser light, and is arranged between the optical fiber emission end and the processing lens 16. Reference numeral 17 denotes a workpiece such as a thin steel plate or an aluminum thin plate.

The power laser beam 2 emitted from the output end of the optical fiber 6 is condensed by a processing lens 16 and irradiated on a workpiece 17 to be cut and welded. At the time of processing, reflected light of power laser light and light when metal is melted and evaporated from the processed portion are generated. The light generated when the metal is melted and evaporated contains a large amount of light 18 (hereinafter referred to as return light) in the visible light region. This return light 18 is not only radiated to the periphery of the processing portion, but also returns along the optical path of the power laser beam 2 applied to the workpiece 17. That is, the processing lens 16
Then, the light 18 returns to the direction of the optical fiber 6 and travels. However, since the visible light selective reflection means 15 is provided between the processing lens 16 and the optical fiber emission end, the return light 1
8 is cut. Since the return light 18 is prevented from returning into the optical fiber 6 as described above, a trouble of the optical fiber 6 is detected.

That is, if the power laser beam 2 is irradiated when the middle part of the optical fiber 6 is broken or dust is attached to the incident end face or the outgoing end face of the fiber 6, the power laser beam will The light 2 is scattered or reflected, and dust or the like in an abnormal portion or the polymer coating material 6a of the fiber 6 is burned to emit light, and the emitted secondary light 7 as visible light is emitted from the incident end face of the fiber 6. The light is emitted in reverse. The emitted secondary light 7 is transmitted to the condenser lens 5
Then, the light is reflected by the mirror 4, passes through the filter 8, and is received by the light receiving detector 9 that detects visible light. The visible light detector 9 converts the output of the secondary light 7 into an electric signal, and
The electric signal of the secondary light 7 amplified by the amplifier 10 is input to the comparator 12 at a voltage division ratio of the resistors 11a and 11b. The voltage of the secondary light 7 input to the comparator 12 is compared with a reference voltage of a set level from the reference value circuit 13, and when the voltage of the secondary light 7 reaches the level of the reference voltage, the voltage of the comparator 12 An electric signal is sent from the output terminal to the shutter drive circuit 14, and the shutter drive circuit 14 operates to close the shutter mechanism 3 and cut off the irradiation of the power laser light 2. As described above, when an accident in optical transmission occurs in the optical fiber, the accident is immediately detected and the power laser light 2 is detected.
Can be cut off, and radiation of the power laser beam 2 can be prevented.

In the first embodiment, the visible light selective reflection means 1 reflects visible light and transmits almost 100% of the power laser light.
5 is disposed between the optical fiber output end and the processing lens 16, but this position may be any position between the optical fiber output end and the workpiece 17. Further, instead of inserting a visible light selective reflection filter, visible light is reflected on at least one surface of the processing lens 16 and the power laser light is almost one.
The same effect can be obtained by applying a coating that transmits 00%.

Embodiment 2 FIG. FIG. 2 is a configuration diagram of the visible light selective reflection means 15 according to the embodiment of the present invention. In the figure, 20 is an optical glass, 21 is an anti-reflection film formed on the opposite surface of the visible light selective reflection means 22 and transmitting almost 100% of the power laser light 2, and 22 is a visible light formed on one surface of the optical glass 20. This is selective reflection means. 22a is a high refractive index body, and 22b is a low refractive index body.

The characteristics of antireflection and selective reflection of visible light can be reduced or emphasized by forming a material having an appropriate refractive index on the optical glass 20 by vapor deposition of a required thickness or the like to reduce the difference between the optical glass 20 and air. Is obtained. An appropriate refractive index and an appropriate thickness can be obtained by calculation from the phase condition and the amplitude condition of light.

When a metal is cut and welded in the configuration shown in FIG. 1 using a YAG laser (wavelength λ = 1064 nm) and an optical fiber, the disconnection of the optical fiber is detected by visible light (secondary light 7) from the disconnected portion. The method requires a filter that cuts back light 18 (light in the visible light region (wavelength λ = 400 nm to 800 nm)). One of the thin film configurations having an optical property of selectively reflecting light in the visible light region is that the product of the product of the refractive index (n) and the film thickness (d), n · d, is λ / 8, λ / 4, λ / 4 ... λ / 4, λ / 4
The high refractive index bodies 22a and the low refractive index bodies 22b may be alternately formed as shown in FIG.

The details of the thin film configuration will be described below. In FIG. 2, for example, the film thickness (d
h) is (λ / 8) / nh. Here, λ is, for example, 6
00 nm, nh is the refractive index of the high refractive index body 22a. The film thickness (dL) of the low-refractive-index body 22b thereon is (λ / 4) /
nL. Here, λ = 600 nm, nL is the refractive index of the low refractive index body 22b. Further, the film thickness (dH) of the high-refractive-index body thereon is (λ / 4) / nH. Where λ = 60
0 nm and nH are the refractive indexes of the high refractive index body 22a. Hereinafter, the film (thickness dL) of the low refractive index body 22b and the high refractive index body 22a
(Thickness dH) is repeated, and finally the high refractive index body 22a
(Film thickness dh) is formed.

With the above-mentioned film configuration, the ratio of zero transmittance in the visible light region as an optical characteristic is 90% or more, and the high refractive index body 22a, which is a thin film material that transmits 99% or more of the YAG laser light, has a low refractive index. Regarding the difference in the refractive index of the refractive index body 22b (hereinafter referred to as the difference in the refractive index) and the number of layers thereof, FIG. 3 shows the case where the low refractive index body 22b (NaF; sodium fluoride, refractive index n = 1.34) is fixed. The ratio in which the visible light region when the high refractive index body 22a is changed becomes zero percent transmittance (hereinafter referred to as the visible light region ratio) and the transmittance of the power laser light (hereinafter referred to as the laser transmittance). It is shown. As shown in the figure, when the difference in the refractive index increases, the ratio of the visible light region increases. An example of this relationship is spectral characteristics (wavelength-transmittance relationship).
FIG. Further, as the number of layers increases, the laser transmittance increases. FIG. 5 shows an example of this relationship by spectral characteristics. As described above, based on the optical characteristics in which the visible light region is 90% and the laser transmittance is 99% or more, FIG.
More conditions for the difference in the refractive index and the number of thin film layers are set. Therefore,
In the 19th layer, the difference in the refractive index is 2.9 (point (a) in FIG. 3).
3.75 (point (b) in FIG. 3), and the refractive index difference of the 21st layer is 3.2 or more (point (c) in FIG. 3).

Among the existing materials as vapor deposition materials constituting the vapor deposition film of the visible light selective reflection means, those having the lowest refractive index are those having the highest refractive index of NaF (sodium fluoride, refractive index n = 1.34). Is (PbTe (lead telluride, refractive index n = 5.50). Therefore, the maximum difference in the refractive index is 4.16 as in the present embodiment. As shown in the graph of the refractive index difference of 4.16, the YAG laser light is transmitted by 99% or more and visible light (wavelength 4
(00 nm to 800 nm) is 100% reflected and cut off.
Therefore, a vapor deposition film configuration having a refractive index difference of 2.9 to 4.16 is suitable. In addition, the number of layers is at least 19 or more, and the maximum is about 40 layers in terms of cost. As described above, the visible light selective reflection means 15 can be manufactured at low cost while transmitting the laser light efficiently and reliably reflecting the return light.

Embodiment 3 FIG. FIG. 6 is a configuration diagram showing an optical fiber device for laser transmission according to Embodiment 3 of the present invention. Symbols 1-3,5,6-1
Reference numerals 0, 12 to 14 are the same as or equivalent to the conventional case. Reference numerals 16 to 17 are the same as or equivalent to those in the first embodiment. The optical fiber 6 through which the power laser light 2 is transmitted is coated with, for example, plastic (nylon) 6a. On the coating surface, two twisted enamel-coated copper wires (hereinafter referred to as stranded wires) 30 are spirally wound. Both ends of two strands taken from one end of the optical fiber 6 are connected to lead wires 31.
Note that the other of the two strands is not connected and is open. A voltage circuit 32 is arranged in the middle of the lead wire 31, and a voltage is applied between the two strands. Similarly, a disconnection detecting circuit 33 composed of a resistance and a voltmeter is arranged in the middle of the lead wire 31. The disconnection detection circuit 33 includes the amplifier 1
0, and the output of the amplifier 10 is connected to the comparator 1
2 is connected to one input terminal. The other input terminal of the comparator 12 has a reference value circuit 13 for generating a reference voltage.
Is connected. The output end of the comparator 12 is connected to a shutter drive circuit 14, which operates according to an output signal from the comparator 12 to close the shutter mechanism 3 interposed in the optical path of the power laser light 2. The irradiation of the power laser beam 2 is cut off.

Next, the operation will be described. When the middle portion of the optical fiber 6 is broken and the power laser beam is irradiated, the power laser beam 2 is scattered or reflected at the broken portion, and the stranded wire 30 wound around the optical fiber coating surface is formed.
Is melted and carbonized, and the copper wire is short-circuited, a current flows due to the short-circuit of the stranded wire 30, and a voltage is generated in the disconnection detection circuit 33. When this voltage becomes higher than the voltage generated from the reference value circuit 30, the shutter drive circuit 14 operates to close the shutter mechanism 3 and cut off the irradiation of the power laser beam.

In this embodiment, an enamel-coated copper wire is used as the insulated coated conductor. However, a coating material such as nylon which is easily carbonized, and a conductor having a small electric resistance such as aluminum can be used. In addition, the conductors may be arranged adjacent to each other in parallel instead of twisted. Also,
The insulated wire is spirally wound around the optical fiber,
In short, the same effect can be obtained if the insulated conductor is uniformly arranged with respect to the optical fiber to the extent that the disconnection of the optical fiber can be detected.

Embodiment 4 FIG. FIG. 7 is a configuration diagram showing an optical fiber device for laser transmission according to Embodiment 4 of the present invention. Symbols 1-3,5,6-1
Reference numerals 0, 12 to 14 are the same as or equivalent to the conventional case. Reference numerals 16 to 17 are the same as or equivalent to those in the first embodiment. 31 to 33 are the same as or equivalent to the third embodiment. The optical fiber 6 through which the power laser light 2 is transmitted is covered with a plastic (nylon) 6a.
40 is an insulating plate (polyethylene sheet, thickness 0.05m)
m) An insulating plate in which 40b is sandwiched between copper foils 40a is a sandwiched copper foil sheet (hereinafter, referred to as a copper foil sheet), and FIG. The surface of the copper foil 40a on the side of the optical fiber 6 is coated with a laser light antireflection member 40c for increasing the absorption of laser light as a paint.
The copper foil sheet 40 is disposed so as to surround the entire optical fiber 6 covered with the plastic coating 6a. The copper foil sheet 40 is located at one end of the optical fiber 6 at the position of the insulating plate 40.
The copper foil 40 a sandwiching “b” is connected to the lead wire 31. The other side of the copper foil sheet 40 is not connected and is in an open state. A voltage circuit 32 is arranged in the middle of the lead wire 31 and a voltage is applied between two copper foils. Similarly, a disconnection detecting circuit 33 composed of a resistance and a voltmeter is arranged in the middle of the lead wire 31. The disconnection detection circuit 33 is connected to the input terminal of the amplifier 10, and the output terminal of the amplifier 10 is connected to one input terminal of the comparator 12. Comparator 12
Is connected to a reference value circuit 1 for generating a reference voltage.
3 are connected. The output terminal of the comparator 12 is connected to the shutter drive circuit 14 and the shutter drive circuit 1
Reference numeral 4 operates according to an output signal from the comparator 12, and closes the shutter mechanism 3 interposed in the optical path of the power laser light 2 to cut off the irradiation of the power laser light 2.

Next, the operation will be described. When the middle part of the optical fiber 6 is broken and the power laser light is irradiated, the power laser light 2 is scattered or reflected at the disconnection point, and the antireflection member 40c of the copper foil sheet 40 wound around the entire surface of the optical fiber coating is removed. Formed copper foil 40a
Is heated, the insulating layer between the copper foils is melted and carbonized, and the copper foils are short-circuited. Next, the copper foil is melted, and the copper foil and the copper foil are connected and completely short-circuited. A current flows due to the short circuit of the copper foil, and a voltage is generated in the disconnection detection circuit 33. When this voltage becomes higher than the voltage generated from the reference value circuit 30, the shutter drive circuit 14 operates to close the shutter mechanism 3 and cut off the irradiation of the power laser beam.

In this embodiment, polyethylene is used as the insulating plate. However, the insulating plate may be made of vinyl chloride or the like which is easily carbonized, and the metal foil may be made of aluminum or the like having a small electric resistance. Further, in the present embodiment, the entire optical fiber is wrapped by one copper foil sheet, but the same effect can be obtained by wrapping the optical fiber with a copper foil sheet on a tape.
The antireflection member 40c is formed by applying a paste of, for example, carbon black or copper oxide powder, but may be formed by another method such as thermal spraying.

[0035]

Since the present invention is configured as described above, it has the following effects.

By installing visible light selective reflection means for reflecting light in the visible region (return light) and transmitting the power laser light between the output end of the optical fiber and the workpiece, the middle part of the optical fiber 6 is broken. Return to an abnormal location such as dust or the like on the input end face or output end face of the fiber 6 and detect the abnormal location of the optical fiber with high accuracy by visible light emitted from the abnormal location without being disturbed by light. It is possible to block the laser light and to prevent the laser light from radiating outside.

Further, when the visible light selective reflection means is manufactured by alternately forming a high-refractive index material and a low-refractive index material, the optimum material combination and the minimum number of layers are used. Light can be transmitted efficiently and return light can be reliably reflected.

A metal foil sheet having an insulating plate interposed therebetween is disposed on the entire surface of the optical fiber to detect a disconnection of the optical fiber transmitting the power laser light, and the resistance between the metal foils is detected. Therefore, disconnection of a long optical fiber can be easily detected, and disconnection of an optical fiber can be reliably detected. Further, the disconnection can be detected with high accuracy without being disturbed by the return light, and the power laser beam can be cut off.

Further, by forming a laser beam anti-reflection member on the surface of the optical fiber of the sheet, the laser beam scattered by the disconnection can be reliably absorbed, and the energy of the laser beam can be transmitted to the sheet.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an optical fiber device for laser transmission according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a visible light selective reflection unit for an optical fiber device for laser transmission according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a visible light selective reflection characteristic of a visible light selective reflection means for an optical fiber device for laser transmission according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing visible light selective reflection characteristics of a visible light selective reflection means for an optical fiber device for laser transmission according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a visible light selective reflection characteristic of a visible light selective reflection means for an optical fiber device for laser transmission according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram illustrating an optical fiber device for laser transmission according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram illustrating an optical fiber device for laser transmission according to a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram showing an insulating plate sandwiched copper foil sheet for an optical fiber device for laser transmission according to Embodiment 4 of the present invention.

FIG. 9 is a configuration diagram showing a conventional optical fiber device for laser transmission.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source 2 Laser light (power laser light) 3 Shutter mechanism 4 Mirror 5 Condensing lens 6 Optical fiber 7 Secondary light 8 Filter 9 Reception detector 10 Amplifier 11a, 11b Resistance 12 Comparator 13 Reference value circuit 14 Shutter drive circuit 15 Visible light selective reflection means 16 Processing lens 17 Workpiece 18 Return light 20 Optical glass 21 Antireflection film 22 Visible light selective reflection film 30 Enamel coated copper wire (stranded wire) 31 Lead wire 32 Voltage circuit 33 Disconnection detection circuit 40 Insulation Plate sandwiched copper foil sheet 40a Copper foil 40b Insulating plate 40c Laser light reflection preventing member

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-108243 (JP, A) JP-A-57-29346 (JP, A) JP-A-56-17303 (JP, A) 341152 (JP, A) JP-A 54-103098 (JP, U) JP-B 57-14584 (JP, B2) JP-B 60-22572 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 26/00 B23K 26/06 B23K 26/08 G02B 6/02

Claims (5)

(57) [Claims] 1. An optical system for transmitting a laser beam through an optical fiber, irradiating a workpiece with the laser beam and processing the laser beam, and when a failure occurs in a transmission path of the laser beam of the optical fiber.
A second detecting unit that detects visible light emitted from the optical fiber, and the detected visible light indicates visible light emitted from an abnormal portion.
In a laser transmission optical fiber device having a means for blocking laser light when a detection level of a next light is reached, a laser beam is transmitted through the optical fiber and a visible light selective reflection means for reflecting visible light emitted during processing of a workpiece is provided by an optical fiber. An optical fiber device for laser transmission, which is provided between a laser light emitting end and a workpiece. 2. The visible light selective reflection means comprises: forming a high-refractive-index thin film on optical glass; alternately stacking a low-refractive-index thin film and a high-refractive-index thin film; Wherein the product of the light refractive index and the film thickness of each thin film is a high light refractive index body in contact with the optical glass and a thin film of the high light refractive index body formed on the outermost side. 2. The optical fiber device for laser transmission according to claim 1, wherein the wavelength is one-eighth of the wavelength of visible light emitted during processing, and the remaining thin film is one-fourth of the wavelength of visible light. 3. The visible light selective reflection means comprises: forming a high-refractive-index thin film on optical glass; alternately stacking a low-refractive-index thin film and a high-refractive-index thin film; When the difference in refractive index between the low- and high-refractive-index bodies is in the range of 2.90 to 4.16, and the total number of thin films is in the range of 19 to 40, 2. The optical fiber device for laser transmission according to claim 1, wherein: 4. A laser beam machine for transmitting a laser beam through an optical fiber, irradiating the workpiece with the laser beam, and processing the laser beam, wherein a protective film is coated so that the laser beam is not radiated to the outside, and the laser beam is transmitted. The entire surface of the optical fiber is covered with a sheet having an insulating plate interposed between metal foils, a voltage is applied between the metal foils, a change in resistance between the metal foils is detected, and the resistance reaches a predetermined level. An optical fiber device for laser transmission, comprising: means for shutting off a laser beam in the case where the optical fiber device is used. 5. An optical fiber device for laser transmission according to claim 4, wherein a laser light antireflection member for absorbing laser light is formed on an optical fiber side surface of the metal foil located on the optical fiber side of the metal foil. .